Single blade fire damper

ABSTRACT

A fire damper for use in small openings comprises a single blade articulated about a hinge within a frame, which blade is movable between an open and closed position. In the open position a fusible link and strap retain the blade. When the link is released a negator extension-type spring mounted on the frame forces the blade to close the opening through the frame. A blade lock mounted on the blade engages the frame to retain the blade in the closed position.

United States Patent [191 McCabe SINGLE BLADE FIRE DAMPER [76] Inventor:Francis J. McCabe, Apt. A-4, North & East Sts., Doylestown, Pa. 18901[22] Filed: Jan. 23, 1974 21 Appl. No.: 435,762

[52] US. Cl. 251/303; 98/86; 137/75;

137/457; 292/121 [51] Int. CI. F16K 17/38; E05C 3/00 [58] Field ofSearch 137/75-77,

[56] References Cited UNITED STATES PATENTS 592,532 10/1897 McCreery98/1 X 758,441 4/1904 Harden 292/121 X 2,287,262 6/1942 Merry 126/287.5X 3,035,810 5/1962 Lowe et al. 251/298 3,165,050 1/1965 Johnson 98/86 X[451 Aug. 12, 1975 FOREIGN PATENTS OR APPLICATIONS 859,442 12/1970Canada 98/86 Primary Examiner--Martin P. Schwadron AssistantExaminer-Richard Gerard Attorney, Agent, or FirmBowie, Benasutti andPreston [57] ABSTRACT A fire damper for use in small openings comprisesa single blade articulated about a hinge within a frame, which blade ismovable between an open and closed position. In the open position afusible link and strap retain the blade. When the link is released anegator extension-type spring mounted on the frame forces the blade toclose the opening through the frame. A blade lock mounted on the bladeengages the frame to retain the blade in the closed position.

5 Claims, 4 Drawing Figures SINGLE BLADE FIRE DAMPER BACKGROUND OF THEINVENTION This invention relates to fire dampers, and more particularly,fire dampers having a single blade to close the opening in an air ductsystem.

In the prior art, multiple blade fire dampers were known having aplurality of z -shaped blades centrally notched at their edges anddisposed within a frame having an inwardly depending flange in suchmanner that the flange was positioned in the notch, so that the bladesstraddled the inwardly depending flange. See for example, my priorco-pending application Ser. No. 192,006, filed Oct. 26, 1971, and nowU.S. Pat. No. 3,814,165. Such dampers were maintained in their openposition with the blades folded by a fusible link and strap or otherlink mechanism. When the link released, the blades fell of their ownweight to an unfolded position closing the damper. In addition, a springcould be used attached to the blades to pull the blades securely shut,so that their flat faces lay against the faces of the inwardly dependingflange of the frame.

In use, the multiple blade straddling-type fire damper tended to remainclosed even under increased hot air pressure due to fire, because thedynamic forces on alternate portions of the blades counteracted oneanother. This desirable feature creates undesirable problems when thedampers will be used in small areas, such as openings down to two inchesin height. For one thing, the multiple blades and hinges are bulky andcut down on the usable area for air flow through the device. Secondly,if the multiple blades are replaced by a single blade, the single bladewill act like a backdraft damper, that is, the force of onrushing hotair will force the blade open in one direction even against the actionof the spring utilized to close it. Of course, if the fire is on theother side, the force of hot air will keep the blade closed. However, itwill be readily apparent that this is an undesirable and unacceptablefeature.

SUMMARY OF THE INVENTION The present invention recognizes andcompensates for these problems. It has as an object to provide maximumair flow in the open condition and maximum air stoppage in the closedcondition.

To accomplish these desirable ends, I have provided a frame with asingle blade mounted internally. The configuration of the blade is suchthat in the open condition it lies within the envelope created by theinwardly depending flange of the frame. In the closed condition, a lockengages this flange and retains the blade, thereby preventing it frombeing forced open by the flow of air.

The above object and other objects will become apparent from thefollowing description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a perspective view of thedevice in accor dance with the preferred embodiment of my inventiontaken as viewed from the left-rear-top of the device 3 FIG. 4 is a viewpartially broken away taken as indicated by the lines and arrows 44 inFIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Although specific forms of theinvention have been selected for illustration in the drawings, and thefollowing description is drawn in specific terms for the purpose ofdescribing these forms of the invention, this description is notintended to limit the scope of the invention which is defined in theappended claims.

Referring to the figures, FIG.,1 showsa device comprising a frame 10 andblade 12 with the bladeretained in the open condition by a strap 14 andfusible link 16 as shown in FIG. 2. The blade is articulated about ahinge member 18 which is suitably affixed to the inside of the frame 10as by spot welding. The hinge member 18 and blade 12 form a continuoushinge of the type described generally in my prior issued patents in thisfield. The hinge member does not extend across the full width of theinterior of the frame. The blade extends across the full width of theopening provided within the frame 10. This opening is somewhat smallerat the front of the device by virtue of a continuous flange 20 whichdepends inwardly from the side walls of the frame 10 all about the frontperiphery.

This device is placed in an air duct in an air handling system in abuilding by any suitable means well known in the art. It functions incase of fire by virtue of the fact that the fusible link 16 melts andfalls apart (as shown in FIG. 3), thereby releasing the strap 14 whichholds theblade and allowing the blade to drop to the closed positionshown in FIG. 3. In order to aid in this action, a coiled spring 22 isprovided fixedly attached at one end (as at 24) to the frame 10 ofthedevice and engaging the face of the blade most remote from the frontflange 20. The springis retained by the lower hook shaped portion 26 ofthe blade. Springs of this type are sometimes referred to in the tradeas negator springs and they have the ability to coil and uncoil uponthemselves as shown in the figures. In this case, the spring exerts aforce against the blade driving it toward the closed position and tendsto maintain the blade in that position.

If a fire was located to the left of the device when viewed as in FIG.3, the hot air passing through the air duct system would tend to forcethe blade to the right against the action of the spring and. open thefire damper. In order to maintain the damper in the closed position Ihave provided a blade lock designated generally 30, FIGS. 3 and 4. Theblade lock consists of L- shaped mounting brackets 32, 34 which aresecurely fastened to the blade 12 by any suitable means, such as byriveting and which are spaced from one another. Within this space alatch member 36 is pivotably mounted about a pin 38 which passes throughthe members 32, 34 and is retained therein by any suitable means such ascrimping it over.

The latch member comprises a substantially flat piece of metal having acurved upper rear surface shown in dotted lines in FIG. 3 and designatedgenerally 40, which terminates in a flat rear end portion 42. This flatrear end portion 42 rests against the face of the blade 12, therebypreventing the latch member 36 from pivoting in a counterclockwisedirection about the pin 38 when viewed as in FIG. 3. The curved portion40 allows the memben36 to be pivoted about the pin 38 in a clockwisedirection when viewed in FIG. 3. This condition is important in thelatching of the device.

The front of the member 36 has a beveled surface 50 terminating at itsoutermost end in a point 51 and at its bottom end in a notch designatedgenerally 52. The arrangement is such that, with the device properlypositioned on the blade 12, the flat end 42 maintains the point 51 abovethe innermost terminus 60 of the flange when viewed in the verticalposition shown in FIG. 3. Thus, as the blade swings from the positionshown in FIG. 2 in a clockwise direction to the position shown in FIG. 3the surface 50 engages the terminus 60 and cams the member 36 in aclockwise direction about the pin 38 until the inwardly depending flange20 enters the slot 52. To provide for positive latching, a leaf spring70 is mounted on the blade in any suitable fashion as by riveting andengages the shoulder 72 on the member 36 to exert a counterclockwiseforce thereon about the pin 38. The leaf spring insures the maintenanceof positive engagement of the member 36 with the flange 20 and thereforethe blade 12 remains in the locked closed position even against theaction of hot air pressure tending to move it in a counterclockwisedirection.

If it is desired to reset the mechanism, the member 36 can be raised ina clockwise direction about the pin 38 against the spring 70 by manualmeans and then the blade can be raised to the position shown in FIGS. 1and 2. Another fusible link can be used on the strap 14 or a variety ofother links may be provided. It should be noted when viewing the deviceas in FIG. 2 that the single blade construction and articulated mountingprovide an arrangement wherein the blade lies within the envelopebounded by the upper wall of the frame and an imaginery line drawnhorizontally when viewed as in FIG. 2 from the lower terminus of theinwardly depending upper flange 20. Such an imaginery line would liedirectly on the lower portion of the strap 14. Thus, the blade does notprovide any obstruction to the free flow of air through the device.

It should also be noted that this device can be mounted horizontallyrather than vertically and the action of the spring 22 and lock meanswill function in a manner identical to that previously described.

It will be understood that various changes in the details, materials andarrangement of parts which have been herein described and illustrated inorder to explain the nature of this invention may be made by thoseskilled in the art within the principle and scope of the invention asexpressed in the following claims.

It will further be understood that the Abstract of the Disclosure setforth above is intended to provide a non-legal technical statement ofthe contents of the disclosure in compliance with the Rules of Practiceof the United States Patent Office, and is not intended to limit thescope of the invention described and claimed herein.

What is claimed is:

1. A fire damper, comprising:

a. a frame, said frame defining a flow passage therethrough and having aflange thereon inwardly depending from the walls thereof;

b. a blade mounted within said frame to articulate about one edge ofsaid blade so as to be movable between open and closed positions withrespect to said frame;

c. spring means mounted to said frame and engaging the free swingingportion of said blade to exert a force thereon to move said blade fromsaid open to said closed position;

d. lock means for securely engaging the frame and the blade in theclosed position to retain the blade in that position, said lock meanscomprising a pivotally mounted latch member and a spring, said latchmember having a free end with a beveled surface thereon and having aslot defined therein, said beveled surface positioned to engage theinwardly depending flange of the frame on movement of said blade from anopen position to a closed position, continued movement thereof to camsaid latch about its pivot to allow said slot to matably engage saidflange in the closed position, thereby producing positive retention ofthe blade in the closed position.

2. The invention of claim 1 wherein said spring engages said latch tourge it in a direction to engage said flange.

3. The invention of claim 1 wherein said latch has a curved portionpermitting pivotal movement in one direction to allow engagement withsaid flange.

4. The invention of claim 3 wherein said latch has an end portionpreventing pivotal movement in the opposite direction beyond apredetermined point, so that said beveled surface will engage saidflange as aforesaid.

5. The invention of claim 1 wherein said blade is shaped and arranged tolie behind said flange and not obstruct the air flow through said devicewhen said device is positioned in an air flow system.

1. A fire damper, comprising: a. a frame, said frame defining a flowpassage therethrough and having a flange thereon inwardly depending fromthe walls thereof; b. a blade mounted within said frame to articulateabout one edge of said blade so as to be movable between open and closedpositions with respect to said frame; c. spring means mounted to saidframe and engaging the free swinging portion of said blade to exert aforce thereon to move said blade from said open to said closed position;d. lock means for securely engaging the frame and the blade in theclosed position to retain the blade in that position, said lock meanscomprising a pivotally mounted latch member and a spring, said latchmember having a free end with a beveled surface thereon and having aslot defined therein, said beveled surface positioned to engage theinwardly depending flange of the frame on movement of said blade from anopen position to a closed position, continued movement thereof to camsaid latch about its pivot to allow said slot to matably engage saidflange in the closed position, thereby producing positive retention ofthe blade in the closed position.
 2. The invention of claim 1 whereinsaid spring engages said latch to urge it in a direction to engage saidflange.
 3. The invention of claim 1 wherein said latch has a curvedportion permitting pivotal movement in one direction to allow engagementwith said flange.
 4. The invention of claim 3 wherein said latch has anend portion preventing pivotal movement in the opposite direction beyonda predetermined point, so that said beveled surface will engage saidflange as aforesaid.
 5. The invention of claim 1 wherein said blade isshaped and arranged to lie behind said flange and not obstruct the airflow through said device when said device is positioned in an air flowsystem.